Delta Persei

Delta Persei (Delta Per, δ Persei, δ Per) is a double star in the northern constellation of Perseus. It has an apparent visual magnitude of 3.01,^[2] making it readily visible with the naked eye. Parallax measurements give it a distance of about 520 light-years (160 parsecs) from the Earth.^[1]

δ Persei

Location of δ Persei (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	03h 42m 55.50426s[1]
Declination	+47° 47′ 15.1746″[1]
Apparent magnitude (V)	3.01[2]
Characteristics
Spectral type	B5 III[3]
U−B color index	–0.51[2]
B−V color index	–0.12[2]
Astrometry
Radial velocity (Rv)	+4[4] km/s
Proper motion (μ)	RA: +25.58[1] mas/yr Dec.: −43.06[1] mas/yr
Parallax (π)	6.32 ± 0.47 mas[1]
Distance	520 ± 40 ly (160 ± 10 pc)
Details
Mass	7.0 ± 0.3[5] M☉
Radius	10.5[6] R☉
Luminosity	2,860[7] L☉
Surface gravity (log g)	3.5[6] cgs
Temperature	14,890[3] K
Rotational velocity (v sin i)	190[8] km/s
Age	50.1 ± 6.8[5] Myr
Other designations
δ Persei, 39 Persei, BD+47 876, CCDM J03429+4748A, FK5 131, GC 4427, HD 22928, HIP 17358, HR 1122, IDS 03171+4930 A, PPM 46127, SAO 39053, WDS J03429+4747A.[9]
Database references
SIMBAD	data

The spectrum of this star matches a stellar classification of B5 III,^[3] which indicates it is a giant star that has evolved away from the main sequence after exhausting the hydrogen at its core. It has about seven times the Sun's mass and has an estimated age of 6.8 million years.^[5] The effective temperature of the outer envelope is 14,890 K,^[3] with the energy being emitted at this temperature giving it the blue-white hue that is a characteristic of a B-type star.^[10] It is rotating rapidly with a projected rotational velocity of 190 km s⁻¹, which gives a lower bound for the actual azimuthal velocity along the star's equator.^[8]

This is most probably a binary star and may be a triple star system. It has an optical companion with an apparent magnitude of +6.17 at an angular separation of 0.330 arcseconds and a position angle of 221°,^[11] but it is uncertain whether this is an optical double star or a gravitationally bound companion. The star has also been categorized as a spectroscopic binary, indicating that it has an orbiting companion that has not been separately resolved with a telescope. Finally, this star may be a member of the Melotte 20 open cluster, which would make it the second-brightest member after Mirfak.^[12]

Observation with the IRAS shows an extended, ring-like feature that may be a bow wave driven by radiation pressure from the star, rather than a bubble being generated by the stellar wind. This feature has an angular size of 15 × 25 arcminutes and a peak temperature of 38 K.^[13] It has an estimated peculiar velocity of more than 30 km s⁻¹, making it a runaway star.^[14]

Name and etymology

• This star, together with ψ Per, σ Per, α Per, γ Per and η Per, has been called the Segment of Perseus.^[15]
• In Chinese, 天船 (Tiān Chuán), meaning Celestial Boat, refers to an asterism consisting of δ Persei, η Persei, α Persei, γ Persei, ψ Persei, 48 Persei, μ Persei and HD 27084. Consequently, the Chinese name for δ Persei itself is 天船五 (Tiān Chuán wu, English: the Fifth Star of Celestial Boat.)^[16]

References

1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
3. Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147, S2CID 14969137
4. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
5. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
6. Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
8. Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590
9. "V* del Per -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-06
10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
11. Fabricius, C.; Makarov, V. V. (April 2000), "Two-colour photometry for 9473 components of close Hipparcos double and multiple stars", Astronomy and Astrophysics, 356: 141–145, Bibcode:2000A&A...356..141F
12. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976
13. van Buren, Dave; McCray, Richard (June 1988), "Bow shocks and bubbles are seen around hot stars by IRAS", Astrophysical Journal Letters, 329: L93–L96, Bibcode:1988ApJ...329L..93V, doi:10.1086/185184
14. van Buren, Dave; Noriega-Crespo, Alberto; Dgani, Ruth (December 1995), "An IRAS/ISSA Survey of Bow Shocks Around Runaway Stars", Astronomical Journal, 110: 2914, Bibcode:1995AJ....110.2914V, doi:10.1086/117739
15. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 331. ISBN 0-486-21079-0. Retrieved 2012-09-04.
16. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日

External links

• Al-Thurayya